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<div id="version" align=right><b>petsc-3.4.2 2013-07-02</b></div>
<A NAME="PCKSP"><H1>PCKSP</H1></A>
Defines a preconditioner that can consist of any <A HREF="../KSP/KSP.html#KSP">KSP</A> solver. This allows, for example, embedding a Krylov method inside a preconditioner.
<H3><FONT COLOR="#CC3333">Options Database Key</FONT></H3>
<DT><B>-pc_use_amat </B> -use the matrix that defines the linear system, Amat as the matrix for the
inner solver, otherwise by default it uses the matrix used to construct
the preconditioner, Pmat (see <A HREF="../PC/PCSetOperators.html#PCSetOperators">PCSetOperators</A>())
<br>
<P>
<P>
<P>
Notes: Using a Krylov method inside another Krylov method can be dangerous (you get divergence or
the incorrect answer) unless you use <A HREF="../KSP/KSPFGMRES.html#KSPFGMRES">KSPFGMRES</A> as the other Krylov method
<P>
Developer Notes: PCApply_KSP() uses the flag set by <A HREF="../PC/PCSetInitialGuessNonzero.html#PCSetInitialGuessNonzero">PCSetInitialGuessNonzero</A>(), I think this is totally wrong, because it is then not
using this inner <A HREF="../KSP/KSP.html#KSP">KSP</A> as a preconditioner (that is a linear operator applied to some vector), it is actually just using
the inner <A HREF="../KSP/KSP.html#KSP">KSP</A> just like the outer <A HREF="../KSP/KSP.html#KSP">KSP</A>.
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../PC/PCCreate.html#PCCreate">PCCreate</A>(), <A HREF="../PC/PCSetType.html#PCSetType">PCSetType</A>(), <A HREF="../PC/PCType.html#PCType">PCType</A> (for list of available types), <A HREF="../PC/PC.html#PC">PC</A>,
<BR><A HREF="../PC/PCSHELL.html#PCSHELL">PCSHELL</A>, <A HREF="../PC/PCCOMPOSITE.html#PCCOMPOSITE">PCCOMPOSITE</A>, <A HREF="../PC/PCSetUseAmat.html#PCSetUseAmat">PCSetUseAmat</A>(), <A HREF="../PC/PCKSPGetKSP.html#PCKSPGetKSP">PCKSPGetKSP</A>()
<P>
<P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>intermediate
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/ksp/pc/impls/ksp/pcksp.c.html#PCKSP">src/ksp/pc/impls/ksp/pcksp.c</A>
<BR><A HREF="./index.html">Index of all PC routines</A>
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